Process and abrasive for finishing granite



Patented Jan. 3, 1939 UNITED STATES PROCESS AND ABRA SIVE FOR FINISHING GRANITE Robert B. Perry, Waterbury, Vt., assignor to Rock of Ages Corporation, of Vermont Barre, Vt., a. corporation No Drawing. Application March 26, 1938 Serial No. 198,165

3 Claims.

This invention relates to the production of finished surfaces on blocks of granite, such as are used for memorial or structural purposes.

It is the general object of my invention to provide a novel process by which a lighter, smoother and generally more satisfactory finish on granite may be attained.

A further object is to provide an improved abrasive for use in the final step in my improved finishing process.

Myinvention further relates to certain ordered procedure which will be hereinafter described and more particularly pointed out in the appended claims.

In producing a finished surface on granite by my improved process, a sawed or machined granite surface is first produced by any usual apparatus, and this sawed or machined surface is then rough ground with steel shot or crushed steel un- 20 til the surface is reasonably uniform.

During this rough grinding operation, a mixture of granite dust, particles of steel and other waste materials accumulates on the stone, which mixture is known in the trade as mud. One eflect of the steel shot or crushed steel, mixed with mud, on the granite is to give the granite surface a bluish cast or color, which is much darker than the desired finish.

The next step in my improved process is to remove all of the steel and mud from the stone by thorough washing, after which the rough ground and washed surface is subjected to a second or finish grinding operation in which an intimate mixture of small steel shot and tale is used 35 as the grinding material.

This second or finish grinding operation is relatively brief but is continued long enough to produce a surface which is smooth to the touch,

which has the desired light color, almost white. and which furthermore brings out the grain or texture of the granite to an unusual degree. In color, a surface produced by my improved process is as light as hammered or bushed work and is at the same time much smoother.

The finish produced by use of this mixture of steel and tale is superior to any finish which can be produced by the use of steel alone, as the talc apparently acts in the nature of a lubricant between the steel and the granite, with the advantageous results above set forth.

Having thus described my invention and the advantages thereof, I do not wish to be limited to the details herein set forth, otherwise than as set forth in the claims, but what I claim is:

1. The process of giving a block of granite a smooth light-colored finished surface which consists in providing a rough-finished uniform surface, thoroughly washing said surface, and then giving said surface a final grinding with an intimate mixture of small steel shot and tale.

2. The process of finishing a granite surface which consists in machining said surface, roughfinishing said surface by grinding with small loose portions of metal, such as steel shot or crushed steel, until a uniform surface is attained, washing the steel and mud from the surface, and then givingsaid surface a final grinding with an intimate mixture of small steel shot and talc, where-- by a smooth and lighter colored finished surface is attained, in which surface the grain of the stone is effectively displayed.

3. An abrasive for use in finishing granite surfaces which is a mixture of small steel shot and talc, intimately commingled.

ROBERT B. PERRY. 

